The overall objectives of this project are to investigate the biological properties of molecules labeled using bifunctional chelates, in both tissue culture and tumor mice, and to study the most promising tumor imaging agents in human cancer patients. The aim is to develop clinically useful tumor localizing radiopharmaceuticals. For the current year the goals were: 1) to determine the in vivo tumor localizing properties of the new bleomycin conjugates BLEDTA I and BLEDTA II; 2) to study the mechanism of uptake of these compounds by tumor cells in tissue culture including the effect of charge and stereoisomeric configuration; 3) to carry out a clinical trial of BLEDTA I labeled with In-111 to determine the sensitivity for tumor detection as well as ease and practicality of clinical use. The animal and human studies have shown the BLEDTA compounds to be reliable and clinically useful tumor imaging agents. The discovery and early characterization of a bleomycin receptor on human neutrophils has provided us with a powerful tool for the investigation of the mechanism of bleomycin transport and concentration in cells.